VW Passat 1.9TDI from 1997 still goes at around 5 litres for 100 km
Seat Ibiza 1.9 SDI from 2004 goes even lower as 4 litres for 100km
My Thinpad X200s from 2008 upgraded the hard drive to a SSD, does everything and more.Runs MintKDE flawlessly.
All second hand, best purchases ever.at least for me.

I rarely buy second hand, in most cases people here dontīt know how to preserve their old/used things Iīm willing to buy second hand. Also I never sold something I had used for more than few days, I find myself easily attached to all kind of technical stuff I use on daily basis, when they become old/slow/useless I clean and store them somewhere in basement of my house and buy new/modern replacement. I don`t have heart to sell my old stuff for few bucks to some unknown person.

Honestly, I buy a ton of used stuff. Only thing new in my current computer build at all is my keyboard, mouse, and psu. Which I got all 3 for a steal!
I have quite good luck with buying used stuff.
I build my mustang with alot of used stuff as well. Parts from the junkyard.

An example, parking brake stradle cable new $76
Junkyard $6. And is practically near new condition.

My car.... It was "ridden hard and put up wet" but it's been reliable for the most part. Only needed a few minor repairs. Alternator, fuel pump, clutch master cylinder, shocks, struts, rear cross-member, heater-box and evaporator, and a reseal of the rear body. Wife, though damaged and slightly used, was in better shape when I got her....

Most used (relatively large purchases in my eyes)
~ 1997 Honda Prelude with 142k miles on it (sold it)
~ 2009 Subaru Legacy 34k miles on it (love my Legacy I just wish it was a GT)
~ 2000 Gibson SG Standard in Ferrari Red
~ My Gtx 570, bought it from my friend after he had it for 1-2 years. I've never bought a used pc component beforehand.